Did Wave ever really live, though? I know it had its vocal fans for whatever reason, but most people never understood what it was, even if they had heard of it and tried to use it (like myself).
Wave was a layer that live on top of a modified Jabber/XMPP chat server. It sent extra meta data to your messaging client. Depending on your client and meta data sent your client could download JavaScipt applets you authorized. The applet would render the meta data into something like an iFrame to show a Google Document or a PacMan game. Also you could create a separate messaging thread from a single comment but still have a link to parent thread (ala #Slack now.)
The branching comments, embedded documents, and ability to create mini applets were the big selling points. But the feature were never well explained and internal implementation was a nightmare. As people could still hook in Jabber with client it was also creating issues with spamming and hacking.
The interesting bit of Wave wasn't the product but the underlying framework components they created for it e.g. salmon protocol and the pubsub system.
They made many of the components needed to create an open source federated social networking system where separate implementations could interact with each other. So for example your user on your company's twitter/fb hybrid could have threaded conversations with other users across other organisation's fb clones (obviously with access control).
This could have been exactly the killer functionality to topple centralised proprietary Twitter and Facebook. Google should have thrown everything into it, could have turned out as impactful as hypertext.
